Abstract
Fractal scaling is a common property of temporal change in various modes of animal behavior. The molecular mechanisms of fractal scaling in animal behaviors remain largely unexplored. The nematode C. elegans alternates between swimming and resting states in a liquid solution. Here, we report that C. elegans episodic swimming is characterized by scale-free kinetics with long-range temporal correlation and local temporal clusterization, namely consistent with multifractal kinetics. Residence times in actively-moving and inactive states were distributed in a power law-based scale-free manner. Multifractal analysis showed that temporal correlation and temporal clusterization were distinct between the actively-moving state and the inactive state. These results indicate that C. elegans episodic swimming is driven by transition between two behavioral states, in which each of two transition kinetics follows distinct multifractal kinetics. We found that a conserved behavioral modulator, cyclic GMP dependent kinase (PKG) may regulate the multifractal kinetics underlying an animal behavior. Our combinatorial analysis approach involving molecular genetics and kinetics provides a platform for the molecular dissection of the fractal nature of physiological and behavioral phenomena.
Highlights
Fractal scaling is a common property of temporal change in various modes of animal behavior
The swimming activity in WormFlo chambers decayed with kinetics similar to that seen in animals cultured without energy source in substantially larger (2 × diameter, 23 × volume) 96-well plate wells (Movie S3); and the activity was sustained in animals cultured in WormFlo with energy sources (Fig. S5A and Movie S4)
For molecular dissection of the multifractal kinetics C. elegans episodic swimming, we studied the egl-4(n479) mutant, in which the temperature sensitive n479 allele of egl-4 is associated with a defect in conventional episodic swimming characterized by lengthened continuous swimming periods and a reduced frequency of resting[22,24]
Summary
Fractal scaling is a common property of temporal change in various modes of animal behavior. We report that C. elegans episodic swimming is characterized by scale-free kinetics with long-range temporal correlation and local temporal clusterization, namely consistent with multifractal kinetics. Multifractal analysis showed that temporal correlation and temporal clusterization were distinct between the actively-moving state and the inactive state These results indicate that C. elegans episodic swimming is driven by transition between two behavioral states, in which each of two transition kinetics follows distinct multifractal kinetics. Many arrhythmic changes of behavioral and physiological activities in a great variety of animal species, including humans are reported to show self-similar and scale-free structures, which is an indicative for fractal s caling[3,4,5] (Fig. S1 and Supplemental Information). Of animal activities based on fractal scaling with genetic analyses of animal behavior Such a combinatorial approach remains to be explored. PKG is considered to be a conserved modulator of animal behavior[29,30]
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